The vehicle tire has a tread with a function of establishing rolling contact with a surface, such as a roadway. The tread is formed with a tread pattern featuring divergent grooves for providing the tread with tread blocks, i.e. the tread comprises blocks and grooves. The grooves have a purpose of enabling the water, possibly present on the surface, to flow in a way to establish a contact as good and tight as possible between the tread, more specifically a tread block, and the roadway. The water present on the surface is displaced by means of the grooves from under the tread blocks primarily sideways of the tire. Some of the water remains within confines of the grooves, whereby the tire rolls over the water in such a way that, at the rolling portion, the water runs along the grooves alongside the tread blocks past the rolling portion. Vehicle tires in road traffic service are legally required to have sufficiently deep grooves for the safe operation of a vehicle in fluctuating weather conditions.
The flow rate of water in a groove is naturally strongly dependent on the driving speed of a vehicle. The effect of grooves on the flow rate and volume flow of water is a significant factor in terms of contact between water and tire. In the event that the grooves are not able to displace a sufficient amount of water from the rolling portion, i.e. from the contact patch, the tire will climb onto the top of a water cushion present on the surface, for so-called aquaplaning, whereby the friction between tire and surface disappears almost completely. Hence, it is an objective to provide such a design for the grooves that the flow of water in a groove is as efficient as possible.
In prior art, the subject matter is discussed in U.S. Pat. No. 4,641,696, which discloses a tread pattern, which has a determined rotating direction and which is intensely divided with grooves into tread blocks, and which has obliquely disposed transversal grooves guiding water towards a sidewall of the tire. The publication also suggests that the apices of blocks can be inclined in order to avoid premature wear-and-tear and ripping and chipping of the blocks.
The prior art also discloses WO 2013/092206 A1, which presents a transverse groove commencing from the middle of a tread block and having its beginning inclined in two directions.
The prior art further discloses EP 2 316 666 A2, which also presents one embodiment of a transverse groove inclined in two directions from the middle of a profile block.